The present invention relates in general to the design and construction of tubing assemblies which are used in closed fluid systems such as those associated with the drain-back of oil into the engine block of an internal combustion engine. More specifically, the present invention relates to the design of a relatively rigid oil drain-back tube for an engine block which is designed for a press fit into a bore in the engine block.
A turbocharged engine requires a steady flow of clean lubricating oil from the engine to the bearings of the turbocharger. It is just as important to return the lubricating oil from the turbocharger to the engine crankcase to ensure that a sufficient supply of oil is available for circulation throughout the engine and turbocharger. A turbocharger oil drain tube provides the conduit for returning the lubricating oil to the engine crankcase.
One style of design for connecting a drain tube to the engine block is to create a receiving bore in the block and a relatively rigid drain tube which is designed to be press fit into the receiving bore. There are though certain problems with this type of design. Typically the drain-back tube has a relatively thin wall and a relatively poor (rough) surface finish, in a microscopic sense, which results in gaps between the bore in the block and the outer diameter surface of the drain-back tube. While the outside diameter of the drain-back tube would appear to be relatively smooth to the touch, the reference to a relatively poor or rough surface finish is more on a microscopic level, but the roughness is still sufficient to result in the creation of various separation gaps. The result of these gaps is the possibility for oil leakage through the press fit region.
While the addition of a sealant at the tube-to-bore interface has in certain cases been tried, the manufacturing sequence is such that the use of sealants which cure quickly are ineffective. In practice, the sealant of choice cures in approximately one minute. However, subsequent to the cure of the sealant, the installed drain tube may need to be turned in the bore in order to orient the other end of the drain tube toward the mating part. The turning or twisting of the drain tube within the bore after the sealant has set up causes the seal to break and the possibility of fluid leakage remains.
The present invention solves the problems of the existing tube-to-block interface by creating a groove in the drain-back tube for receipt of an O-ring seal. On one side of the groove is an insertion portion of the tube which is typically a sliding fit but not a press fit. On the opposite side of the groove is a slightly larger outside diameter which establishes a press fit assembly with the bore in the engine block. The drain tube uses the O-ring seal in combination with the press fit for a leak-free interface. Since a cured sealant is not used, the drain tube is able to be turned or twisted in the bore for aligning the opposite end without losing the leak-free interface. Since the dimensioning of the existing drain tube is substantially unaffected by the modification of adding an O-ring groove, the present tooling which creates the bore in the engine block and the drain tube is substantially the same as before the present invention.
Over the years, various designs for fluid tubes and seals have been invented and the following list of patents is believed to provide a representative sampling of these earlier designs.
U.S. Pat. No. PATENTEE ISSUE DATE 3,001,804 Tomlinson et al. Sep. 26, 1961 3,064,983 Halterman Nov. 20, 1962 4,066,281 De Bonis Jan. 3, 1978 4,129,503 Joseph Dec. 12, 1978 4,268,046 Nisper May 19, 1981 4,559,782 Ritchey et al. Dec. 24, 1985 4,657,188 Crane et al. Apr. 14, 1987 4,705,303 van Aspert Nov. 10, 1987 5,261,237 Benson Nov. 16, 1993 5,402,643 Buchanan et al. Apr. 4, 1995 5,411,114 Bedi et al. May 2, 1995
While a variety of designs are represented by the patents listed above, the claimed invention of the present invention is directed to a structure which is novel and unobvious.